Conventional thread-protecting elements in the form of a helical-shaped, wound wire serve for strengthening the receiving threads of structural members composed of materials of relatively low strength. For this purpose, the thread-protecting element is mounted in the receiving threads, whereupon the screw can then be rotated into the thread-protecting element.
For threading the thread-protecting element into the receiving threads, two types of assembly are customary. With the one type of assembly, the helical-shaped wire is provided with a notch for pulling, using which a special tool pulls the helical-shaped wire along and rotates into the receiving thread, see, for example, U.S. Pat. No. 4,563,119, U.S. Pat. No. 4,645,398, U.S. Pat. No. 4,553,303, etc. With the other type of assembly, the helical-shaped wire is provided on one end with a diagonally running pin for pulling, using which, in turn, a special stool pulls the helical-shaped wire along and through this, rotates it into the receiving thread, see, for example, U.S. Pat. No. 2,152,681, U.S. Pat. No. 2,363,663, etc. The notch for pulling results in a modification of the cross section of the wire, which makes the winding process more difficult. The pin for pulling has the disadvantage that, after the assembly, it must be broken and removed. In each case, an elaborate and costly special tool is required for mounting the helical-shaped wire into the receiving thread.